The paper “Laser action in organic semiconductor waveguide and double-heterostructure devices”, Nature, vol. 389, 362-364, 1997, by V. G. Kozlov, V. Bulovic, P. E. Burrows, S. R. Forrest, describes laser waveguides for organic semiconductor lasers having an optical grating which provides distributed feedback of laser light, and is therefore referred to as distributed feedback grating or DFB grating. DFB gratings are periodic structures having dimensions on the order of 10 nm to 1 μm which are formed in the substrate. In the simplest case, a periodic line grating is formed in the substrate.
According to V. G. Kozlov, V. Bulovic, P. E. Burrows, M. Baldo, V. B. Khalfin, G. Parthasarathy, S. R. Forrest, Y. You, M. E. Thompson, “Study of lasing action based an Forster energy transfer in optically pumped organic semiconductor thin films”, J. Appl. Phys., vol. 84, 4096-4108, 1998, the life of organic semiconductor lasers is mainly limited by oxidation. Therefore, the operation of such an organic semiconductor laser in practice requires encapsulation of the laser dyes to protect them from photo-oxidation with atmospheric oxygen. According to J. Haisma, N. Hattu, J. T. C. M. Pulles, E. Steding, J. C. G. Vervest, “Direct bonding and beyond”, Appl. Opt., vol. 46, 6793-6803, 2007, a covering suitable for this purpose can be affixed by bonding with a substrate on which the semiconductor laser is formed.
The dissertation entitled “Organische Halbleiterlaser auf Basis Photonischer Kristalle (Organic semiconductor lasers based on photonic crystals” by M. Stroisch, University of Karlsruhe, 2007, describes how organic semiconductor lasers can be produced on different substrates, including polymer substrates.
M. Punke, “Organische Halbleiterbauelemente für mikrooptische Systeme (Organic semiconductor devices for micro-optical applications)”, dissertation, University of Karlsruhe, 2007, uses a substrate made of polymethyl methacrylate (PMMA) for the organic semiconductor laser. The substrate contains UV-induced waveguides, such as are described by P. Henzi, D. G. Rabus, U. Wallrabe, J. Mohr in “Fabrication of Photonic Integrated Circuits by DUV-induced Modification of Polymers”, Proc. SPIE 5451, 24-31, 2004. Here, the coupling of the laser light into the passive waveguide is accomplished by evanescent field coupling. In this manner, laser light can indeed be coupled into the waveguides, but simulations show that the power coupled into a multimode waveguide is no more than about 30%. Moreover, this arrangement cannot be covered because the laser layer is vapor-deposited on the substrate, and the resulting height differences on the substrate make it impossible to apply a covering.